Paper transporting apparatus

ABSTRACT

A paper-transporting apparatus is used for transporting recording paper. A paper-transporting device is movable between a loading position where the paper-transporting unit has been completely attached into a chassis and an unloading position where the paper-transporting unit has been completely drawn out of the chassis. A guide member that supports the paper-transporting device and guides the paper-transporting device between the loading position and the unloading position. The paper-transporting device has a cover and a frame that cooperate with each other to form a paper path in which a recording paper is advanced. When the paper-transporting device is at the loading position, a positioning device holds the cover at a certain position with respect to the frame. When the paper-transporting device is at the unloading position, the positioning device does not hold the cover at the certain position with respect to the frame.

FIELD OF THE INVENTION

[0001] The present invention relates to a paper-transporting apparatus for use in an image-recording apparatus, and more particularly to a paper-transporting apparatus for use in an image-recording apparatus capable of printing on both sides of a sheet of paper.

DESCRIPTION OF THE RELATED ART

[0002] A conventional paper-transporting apparatus for use in an image-recording apparatus includes a unit assembly with a paper-transporting mechanism suitable for printing on both sides of a sheet of print paper. The unit includes a frame that supports a drive roller, an upper cover that supports a driven roller, and other associated structural members that fix the upper cover at a predetermined position. The upper cover is provided on a side from which a user can access the paper-transporting mechanism. When a paper jam occurs, the user draws out the unit assembly from the main body of the image-recording apparatus. Then, the user unlocks firmly fixed members manually before opening the upper cover to remove the jammed paper.

[0003] The conventional paper-transporting apparatus for double-sided printing suffers from the following problem. When jammed paper is removed from the unit assembly, the user must first take out the unit assembly from the image-recording apparatus and then open a latching device that holds the upper cover against the frame, before the upper cover can be opened. This operation is complex.

[0004] The unit assembly has drive rollers that are rotatable in forward and reverse directions and a plurality of pressure rollers driven by the drive rollers. The upper cover may be subjected to deformation such as warping or bulge in its middle portion due to the urging force of springs that urge the pressure rollers against the drive rollers. Deformation of the upper cover causes the print paper to become skewed and jammed. Thus, the drive rollers and driven rollers will not apply uniformly distributed pressure to the paper passing between the drive rollers and driven rollers. A non-uniform application of pressure often causes the paper to become skewed or jammed.

SUMMARY OF THE INVENTION

[0005] An object of the invention is to provide a paper transportation apparatus in which when paper is jammed in a paper-transporting mechanism used for double-sided printing, the jammed paper can be removed without difficulty.

[0006] Another object of the invention is to provide a paper-transporting apparatus that minimizes deformation of an upper cover of a paper-transporting mechanism resulting from urging forces of springs that urge pressure rollers, thereby allowing stable paper transportation.

[0007] A paper-transporting apparatus is used for transporting a recording medium. A paper-transporting device movable between a loading position where the paper-transporting unit has been completely attached into a chassis and an unloading position where the paper-transporting unit has been completely drawn out of the chassis. The paper-transporting device having a first section and a second section that cooperate with each other to advance a recording medium. A guide member that supports the paper-transporting device and guides the paper-transporting device between the loading position and the unloading position. A positioning device that holds the first section at a certain position with respect to the second section when the paper-transporting device is at the loading position, the positioning device does not hold the first section at the certain position with respect to the second section when the paper-transporting device is at the unloading position.

[0008] The positioning member includes a first engagement member movable relative to the second section toward the loading position and toward the unloading position. The first engagement member being urged toward the loading position. The second engagement member fixedly provided on the chassis, wherein when the paper-transporting device is moved toward the loading position from the unloading position, the second engagement member engages the first engagement member to prevent the first engagement member from further moving toward the loading position such that the first engagement member moves relative to the second section toward the unloading position to hold the first section at the certain position with respect to the second sections.

[0009] The guide member includes a guide rail, a first projection, and a second projection. The guide rail guides the paper-transporting device between the loading position and the unloading position, the guide rail having a plurality of guide rollers disposed along the guide rail. The first projection is formed on the first section to extend along the guide rail. The second projection is formed on the second section to extend along the guide rail. The first projection and the second projection are placed together and supported on the guide rail such that the first projection and the second projection are movably sandwiched between the guide rollers.

[0010] A pressing member is further formed on the chassis. The pressing member moves into engagement with the second section to position the second section with respect to the first section before the second engagement member engages the first engagement member.

[0011] The pressing member moves out of engagement with the second section after the second engagement member has engaged the first engagement member.

[0012] Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limiting the present invention, and wherein:

[0014]FIG. 1 illustrates a general configuration of an image-recording apparatus having a paper-transporting apparatus according to a first embodiment of the invention;

[0015]FIG. 2 illustrates the operation of a paper guide when an image is printed only on one side of recording paper;

[0016]FIG. 3 illustrates the operation of the paper guide when images are printed on both sides of the recording paper;

[0017]FIG. 4 is a perspective view of the image-recording apparatus, illustrating a paper-transporting unit when the paper-transporting unit is drawn out from the main body of an image-recording apparatus and a cover is rotated to open;

[0018]FIG. 5A is a perspective view illustrating the appearance of the paper-transporting unit when it is drawn out of the image-recording apparatus to an unloading position;

[0019]FIG. 5B shows the paper-transporting unit when the cover has been closed;

[0020]FIG. 6 illustrates the paper-transporting unit when paper-transporting unit is drawn out in a direction shown by an arrow to the unloading position and the cover is opened;

[0021]FIG. 7 is a fragmentary cross sectional side view of a pertinent portion of the paper-transporting unit;

[0022]FIG. 8 is a fragmentary perspective view of a pertinent portion of the paper-transporting unit;

[0023]FIG. 9 is a perspective view illustrating the details of a guide rail;

[0024]FIG. 10 is a perspective view of the cover when it is seen from a direction shown by arrow C of FIG. 6;

[0025]FIG. 11 is a side view of the paper-transporting unit when it has been drawn in a direction shown by arrow B from the image-recording apparatus of FIG. 4;

[0026]FIGS. 12A and 12B are perspective view of cover-locking members;

[0027]FIG. 13 is a side view of the paper-transporting unit when it is being moved in a direction shown by arrow A into the image-recording apparatus from the position shown in FIG. 11;

[0028]FIG. 14 is a side view of the paper-transporting unit when it has been moved completely in the direction shown by arrow A into the image-recording apparatus; and

[0029] FIGS. 15A-15C illustrate the operation of the paper-transporting unit.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0031] First Embodiment

[0032] Construction

[0033]FIG. 1 illustrates a general configuration of an image-recording apparatus having a paper-transporting apparatus according to a first embodiment of the invention.

[0034] Referring to FIG. 1, a cassette-receiving section 4 receives a paper cassette 5 that holds a stack of recording paper 7 therein. A paper-transporting apparatus 8 has a guide means that supports a paper-transporting unit 3 thereon in such a way that the paper-transporting unit 3 can be loaded into and unloaded from the image-recording apparatus 1. The paper-transporting unit 3 transports the recording paper 7 when printing is performed on the both sides of the recording paper. A recording section 2 includes four print engines 2 d-2 g that transfer toner images of corresponding colors sequentially onto the recording paper 7 as the recording paper 7 passes through the path 6 b. A fixing section 2 a is located shortly after the print engine 2 g and fuses the toner images transferred on the recording paper 7 into a permanent image.

[0035] The top page of the stack of recording paper 7 held in the paper cassette 5 is fed into a path 6 a and passes through a path 6 b in the recording section 2. When the recording paper 7 passes through the path 6 b, images are transferred onto the recording paper 7 sequentially and then the recording paper 7 passes through the fixing section 2 a and is finally guided by a paper guide 2 b into an appropriate direction. The recording paper advanced into a path 6 c for singled-sided printing and into a path 6 d for double-sided printing.

[0036]FIG. 2 illustrates the operation of the paper guide when an image is printed only on one side of the recording paper 7.

[0037] When an image is printed only on one side of the recording paper 7, the paper guide 2 b is at a position shown in FIG. 2 so that the printed recording paper 7 advances along the path 6 c and is discharged through a discharging section 2 c.

[0038]FIG. 3 illustrates the operation of the paper guide 2 b when images are printed on both sides of the recording paper 7. When images are printed on both sides of the recording paper 7, the paper guide 2 b is at a position shown in FIG. 3 so that the recording paper 7 passes the fixing unit 2 a and is then advanced along the path 6 d. Subsequently, the transport rollers 13 advance the recording paper 7 into an auxiliary space 6 e provided under the bottom of the paper cassette 5.

[0039] Then, as described later, the transport rollers 13 rotate in a reverse direction so as to advance the recording paper 7 into a path 6 f in the paper transport unit 3 and then into the path 6 b. When the recording paper 7 passes through the path 6 b, images are transferred sequentially onto the backside of the recording paper 7. The recording paper 7 then passes through the fixing section 2 a and then the paper guide 2 b so that the recording paper 7 is finally discharged from the discharge section 2 c.

[0040]FIG. 4 is a perspective view of the image-recording apparatus, illustrating the paper-transporting unit 3 when the paper-transporting unit is drawn out from the main body of an image-recording apparatus 1 and a cover 3 b is rotated to open.

[0041]FIG. 5A is a perspective view illustrating the appearance of the paper-transporting unit when it is drawn out of the image-recording apparatus to the unloading position.

[0042] Referring to FIG. 5A, the cover 3 b has been closed. The paper-transporting unit 3 is supported by a later described guide means that guides the paper-transporting unit 3 to slide in directions shown by arrows A and B.

[0043]FIG. 5B is a fragmentary enlarged perspective view of a bearing section, a portion encircled with a dotted line as shown in FIG. 5A, illustrating.

[0044] The cover 3 b is rotatably supported at four bearings 3 c on a frame 3 a. Shafts 3 d extend through the bearings 3 e of the cover 3 b and bearings 3 c of the frame 3 a so that the cover 3 b is pivotally coupled to the frame 3 a. Thus, the shafts 3 d are in line with one another, so that the cover 3 b can pivot through a predetermined angle about an axis 100 passing through the shafts 3 d.

[0045]FIG. 6 illustrates the paper-transporting unit when paper-transporting unit is drawn out in a direction shown by arrow B to an unloading position and the cover is opened.

[0046] Referring to FIG. 6, a paper-transporting section 3 g defined on the frame 3 a has four sets 10-13 of transport rollers that rotate about axes substantially perpendicular to the axis 100. The paper-transporting section 3 g has ribs 3 v that extend in a direction in which the recording paper is transported. The ribs 3 v guide the recording paper with least friction when the paper passes through the paper-transporting section 3 g. The frame 3 a encloses a drive motor, a motor driving circuit, a clutch, and a belt, not shown, which cooperate one another to drive all the transport rollers in rotation at predetermined timings and speed in the same direction. The frame 3 a has a partially cylindrical surface 3 f formed at the left side of the frame to project outwardly of the frame 3 a such that the transport path has as large a curvature as possible to transport the recording paper without jamming. Four transport rollers 13 are provided such that the transport rollers 13 extend slightly outwardly of the cylindrical surface 3 f.

[0047] The cover 3 b has a projection 3 p that extends laterally outwardly across the entire side portion of the cover 3 b.

[0048]FIG. 7 is a fragmentary cross sectional side view of a pertinent portion of the paper-transporting unit 3.

[0049]FIG. 8 is a fragmentary perspective view of a pertinent portion of the paper-transporting unit 3.

[0050] Referring to FIGS. 7 and 8, the frame 3 a has an edge projection 3 q that projects laterally outwardly from the side portion of the frame 3 a and extends substantially across the side portion. When the cover 3 b has been closed, the projection 3 p is brought into intimate contact with the edge projection 3 q to form a guide rail 3 r. The projection 3 p and the frame 3 a in intimate contact engagement can smoothly slide, being guided between the rollers 28 and 29.

[0051]FIG. 9 is a perspective view illustrating the details of a guide rail 26 of FIG. 4.

[0052] Referring to FIG. 9, the guide rail 26 has a guide groove 26 a that is formed in the middle of the guide rail 26 and extends in the longitudinal direction of the guide rail 26. Three pairs of guide rollers are mounted to the guide rail 26 at predetermined intervals, each pair including a guide roller 28 and a guide roller 29 with the guide groove 26 a therebetween. The guide rollers 28 and 29 are arranged such that circumferential surfaces of the guide rollers 28 and 29 face each other.

[0053] The guide rail 3 r enters the guide groove 26 a in the guide rail 26 so that the guide rollers 28 and 29 can roll on the guide rail 3 r. Thus, the guide rail 3 r is guided to move in the directions shown by arrows A and B.

[0054]FIG. 10 is a perspective view of the cover 3 b when it is seen from a direction shown by arrow C of FIG. 6.

[0055] The cover 3 b has a recess 3 h that is configured to the cylindrical surface 3 f of the frame 3 a. The cover 3 b has a paper-receiving opening 3 s formed beside the recess 3 h. The cover 3 b has a plurality of ribs 3 x formed thereon, the ribs 3 x extending in a direction in which the recording paper is transported. The paper-receiving opening 3 s is a slit-like opening that longitudinally extends across the path 6 d. The recording paper 7 is introduced into the image-recording apparatus 1 through the paper-receiving opening 3 s. There is provided a film 30 that extends from the recess 3 h and across the path 6 d to guide the recording paper 7 that comes into the paper-transporting unit 3 through the paper-receiving opening 3 s. The cover 3 b also has four pressure roller mechanisms 17.

[0056] Each pressure roller mechanism 17 includes the pressure rollers 17 a, a bracket 17 c, and a compression spring 17 d. The four pressure rollers 17 a function as driven rollers in pressure contact with the four transport rollers 13. The bracket 17 c has a shaft 17 b on which the pressure roller 17 a is rotatably mounted. The compression spring 17 d is loaded between the bracket 17 c and the cover 3 b to urge the pressure roller 17 a against the transport roller 13.

[0057] There are provided three sets of pressure roller mechanisms 18A-18C on the underside of the cover 3 b, the three sets of pressure roller mechanisms 18A-18C opposing the three sets 10, 11, 12 of transport rollers provided on the frame 3 a, respectively. Each set of the pressure roller mechanisms 18A-18C includes four sub-mechanisms 18-1 to 18-4 and each set of the transport rollers includes four rollers.

[0058] Each of the four sub-mechanisms 18-1 to 18-4 includes a pressure roller 18 a, a shaft 18 b, and a pair of torsion springs 18 c. The pressure roller 18 a is rotatable on the shaft 18 b. The shaft 18 b is slightly movable relative to the cover 3 b. The torsion springs 18 c, loaded between the shaft 18 b and the cover 3 b, urge the shaft 18 b in a direction away from the underside of the cover 3 b so that when the cover 3 b is closed, the pressure roller 18 a is in pressure contact with the transport roller.

[0059] In this embodiment, the recording paper 7 is sandwiched between the pressure rollers 17 a, 18 a, and the transport rollers 10-13. In stead, a belt or other transporting means may be used to advance the recording paper 7.

[0060] When the paper-transporting unit 3 is in the image-recording apparatus, the paper-transporting unit 3 is supported and guided by the guide rail 26 and a stage 25 (FIGS. 15A-15C). The stage 25 is provided on the inner right side of the image-recording apparatus 1 and supports the right side of the paper-transporting unit 3. The guide rail 26 is provided on the inner left side, depicted by dotted lines in FIG. 4, of the image-recording apparatus 1. The guide rail 26 extends in a direction parallel to the directions shown by arrows A and B.

[0061]FIG. 11 is a side view of the paper-transporting unit 3 when it has been drawn out completely in a direction shown by arrow B from the image-recording apparatus of FIG. 4.

[0062]FIGS. 6A and 6B are perspective view of cover-locking members.

[0063] Referring to FIG. 11, the cover 3 b is pivotally supported on the frame 3 a by means of the shaft 3 d. The cover 3 b rests over a paper-transporting section 3 g (FIG. 6) of the frame 3 a with the pressure rollers 17 a and 18 a (FIG. 10) in contact with the corresponding transport rollers 10-13.

[0064] The cover 3 b has two cover-locking members 14 and 15 provided on a side opposite to the side at which bearings 3 c are provided. The cover-locking members 14 and 15 are slidable in directions shown by arrows A and B. The cover-locking member 15 (14) is urged in the direction shown by arrow A by a compression spring 20 (19) loaded between the cover-locking members 14 (15) and a front wall 3 i of the cover 3 b. The spring (20 (19) is partially received in a spring-receiving hole 15 a. The cover-locking member 15 (14) has an end 15 b urged against an inner wall 3 j of the cover 3 b. The cover-locking member 15 (14) and the compression spring 20 (19) form a cover-locking mechanism that securely locks the cover 3 b to the frame 3 a.

[0065] The paper-transporting unit 3 is housed in an accommodating section having an upper frame 24 formed of a sheet metal. The upper frame 24 has two projections 24 a, two stoppers 24 b, and fitting holes 24 c and 24 d. The stopper 24 b extends downward from the frame 24. Each projection 24 a has a flat surface and beveled surfaces that project downward. Two projections 3 k and 3 w (FIGS. 5A-5B) project upwardly from the cover 3 b of the paper-transporting unit 3. Each of the projections 3 k and 3 w has a flat top surface and beveled surfaces. As the paper-transporting unit 3 is moved into the image-recording apparatus, the projections 24 a are brought into slidable contact with the projections 3 k and 3 w, respectively, thereby preventing the cover 3 b from rotating in a direction that the cover 3 b opens relative to the frame 3 a. The positional relation between the projections 24 a and the projections 3 k and 3 w is such that the projections 24 a are brought out of engagement with the projections 3 k and 3 w when the paper-transporting unit 3 has been completely pushed into the image-recording apparatus. When the paper-transporting unit 3 is pushed into the image-recording apparatus 1, the stopper 24 b engages an engagement portion 15 c formed on the cover-locking member 15. The fitting holes 24 c and 24 d fittingly receive post-lock members 21 and 22 formed on the frame 3 a.

[0066] The cover-locking members 14 and 15 are of the same construction and operate in the same way. The stoppers 24 b cooperate with the cover-locking members 14 and 15 to lock to the frame 3 a or position the cover 3 b relative to the frame 3 a.

[0067] Operation of Cover-Locking Members

[0068] A description will be given of the operation of the cover-locking members when the paper-transporting unit 3 is moved between an unloading position and a loading position. The operation will be described with reference to FIGS. 11, 13, and 14.

[0069] The unloading position is a position where the paper-transporting unit 3 has been completely drawn out from the image-recording apparatus.

[0070] The loading position is a position where the paper-transporting unit 3 has been completely accommodated in the image-recording apparatus.

[0071] As shown in FIG. 11, when the paper-transporting unit 3 has been drawn out of the image-recording apparatus, an end 15 d of the cover-locking member 15 does not project through an opening 3 m formed in the front wall 3 i of the cover 3 b. The user can rotate the cover 3 b in a direction shown by arrow C to a position shown in FIG. 4 and FIGS. 5A and 5B. Then, the user can access the paper-transporting unit 3 to remove jammed paper from the paper-transporting unit 3.

[0072] After the cover 3 b has been closed to a position shown in FIG. 11, the user starts to move the paper-transporting unit 3 in the direction shown by arrow A into the image-recording apparatus 1.

[0073]FIG. 13 is a side view of the paper-transporting unit 3 when it is being moved in a direction shown by arrow A toward the loading position from the unloading position shown in FIG. 11.

[0074] As the user moves the paper-transporting unit 3 into the image-recording apparatus 1, as shown in FIG. 13, the projection 3 k (3 w) formed on the upper surface of the cover 3 b abuts the projection 24 a on the upper frame 24. As the paper-transporting unit 3 moves into the image-recording apparatus, the projection 24 a sliding on the projection 3 k (3 w) as well as pressing the projection 3 k (3 w). With the projection 3 k (3 w) pressed, the cover 3 b is maintained at a certain angular position with respect to the upper frame 24. Then, the engagement portion 15 c of the cover-locking member 15 engages the stopper 24 b on the upper frame 24.

[0075] As a result, the stopper 24 b blocks the engagement portion 15 c, preventing a further movement of the cover-locking member 15 into the image-recording apparatus. As the paper-transporting unit 3 is further advanced in the direction shown by arrow A, the compression spring 20 is progressively compressed and allows the end 15 d to extend through the opening 3 m formed in the cover 3 b.

[0076]FIG. 14 is a side view of the paper-transporting unit 3 when it has been moved to the loading position.

[0077] As the paper-transporting unit 3 is yet further advanced in the same direction, the end 15 d of the cover-locking member 15 extends into an opening 3 n formed in a front wall 3 u of the frame 3 a. Then, the paper-transporting unit 3 is completely placed at the loading position in the image-recording apparatus 1 as shown in FIG. 14.

[0078] When the paper-transporting unit 3 has been completely pushed into the image-recording apparatus, the pair of post lock members 21 and 22 (FIG. 6) slide upward to fit into fitting holes 24 c and 24 d formed in the upper frame 24, thereby locking the paper-transporting unit 3 to the loading position.

[0079] In order to draw the paper-transporting unit 3 out of the image-recording apparatus 1, the pair of post lock members 21 and 22 (FIG. 6) are first caused to slide down and pulled out of the fitting holes 24 c and 24 d. At this moment, the paper-transporting unit 3 pops out in the direction shown by arrow B with the aid of spring force of the compression springs 19 and 20. Thus, the end 15 d of the cover-locking member 15 moves out of the opening 3 n, so that the end 15 b of the cover-locking member 15 again abuts the inner wall 3 j (FIG. 13).

[0080] Then, the user pulls out the paper-transporting unit 3 still further in the direction shown by arrow B until the paper-transporting unit 3 is completely drawn out (FIGS. 4 and 11).

[0081] When the paper-transporting mechanism 3 moves, because the end 15 d enters the opening 3 n, the cover 3 b can be accurately positioned at a predetermined angular position with respect to the upper frame 24. This angular position of the cover 3 b with respect to the frame 3 a is such that the pressure rollers 17 a and 18 a on the cover 3 b are in contact with the transport rollers while being urged by the compression springs 17 d and the torsion springs 18 c. The urging force of these springs applies a predetermined pressure on the rollers so that the recording paper sandwiched between the drive rollers and driven rollers can be smoothly transported.

[0082] When the post lock members 21 and 22 have fitted into the fitting holes 24 c and 24 d, the compressed springs 19 and 20 urge the frame 3 a in the direction shown by arrow B. Therefore, the frame 3 a firmly presses the post lock members 21 and 22 in the direction shown by arrow B, preventing the paper-transporting unit 3 from rattling.

[0083] Printing on Both Sides of the Paper

[0084] The operation of the paper-transporting unit 3 will be described when printing is performed on the both sides of the recording paper.

[0085] FIGS. 15A-15C illustrate the operation of the paper-transporting unit 3.

[0086] Referring to FIGS. 15A-15C, the four transport rollers 13 (FIG. 6) rotate operatively together with other sets 10-12 of transport rollers in a direction as shown by arrow E, so that the recording paper 7 is pulled into the auxiliary space 6 e.

[0087] The recording paper 7 is fed from the paper cassette 5 through the path 6 a of FIG. 1 and then passes through the path 6 b so that printing is performed on a front side of the recording paper 7. Then, the recording paper 7 is guided by the paper guide 2 b into the path 6 d and enters the paper-receiving opening 3 s as shown in a dotted line in FIG. 15A.

[0088] When the trailing end portion of the recording paper 7 passes the film 30, the transport rollers 13 stop rotating temporarily, and subsequently rotate in a direction shown by arrow F, i.e., in a reverse direction. Thus, the recording paper 7 now travels backward to enter the path 6 f and advances along the path 6 f while being sandwiched between the sets 10-12 of transport rollers and the pressure rollers 18 a. Then, the recording paper 7 is discharged through a discharge opening 3 t and enters the path 6 b so that printing is performed on a backside of the recording paper 7. Then, the recording paper 7 is finally discharged through the discharge section 2 c.

[0089] The paper-transporting unit 3 of the aforementioned construction is advantageous in that even when the paper is jammed, the guide rail 26 allows smooth drawing out of the paper-transporting unit 3 from the image-recording apparatus without the cover 3 b fluttering.

[0090] The cover 3 b is securely fastened to the frame 3 a at three sides by three structural elements, i.e., the bearings 3 e, the cover-locking members 14 and 15, and the rollers 28 and 19. This construction minimizes warping of the cover 3 b, maintaining a uniform contact pressure between the four transport rollers 13 in line with one another and the four pressure rollers 17 a (FIG. 10) in line with one another, as well as facilitating smooth transporting of the recording paper.

[0091] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art intended to be included within the scope of the following claims. 

What is claimed is:
 1. A paper-transporting apparatus comprising: a paper-transporting device movable between a loading position where the paper-transporting unit has been completely attached into a chassis and an unloading position where the paper-transporting unit has been completely drawn out of the chassis, said paper-transporting device having a first section and a second section that cooperate with each other to transport a recording medium; a guide member that supports said paper-transporting device and guides said paper-transporting device between the loading position and the unloading position; and a positioning device that holds the first section at a certain position with respect to the second section when said paper-transporting device is at the loading position, said positioning device does not hold the first section at the certain position with respect to the second section when said paper-transporting device is at the unloading position.
 2. The paper-transporting apparatus according to claim 1, wherein the first section includes a drive roller and a second section includes a driven roller, wherein one of the drive roller and the driven roller is resiliently urged against the other of the drive roller and the driven roller to hold the recording medium between the drive roller and the driven roller.
 3. The paper-transporting apparatus according to claim 1, wherein said positioning member includes: a first engagement member movable relative to the second section toward the loading position and toward the unloading position, said first engagement member being urged toward the loading position; a second engagement member fixedly provided on the chassis, wherein when said paper-transporting device is moved toward the loading position from the unloading position, said second engagement member engages said first engagement member to prevent said first engagement member from further moving toward the loading position so that the first engagement member moves relative to said second section to engage the first section.
 4. The paper-transporting apparatus according to claim 1, wherein said guide member includes: a guide rail that guides said paper-transporting device between the loading position and the unloading position, said guide rail having a plurality of guide rollers disposed along said guide rail; a first projection formed on the first section to extend along said guide rail; a second projection formed on the second section to extend along said guide rail; wherein said first projection and said second projection are placed together and supported on said guide rail such that said first projection and said second projection are movably sandwiched between the guide rollers.
 5. The paper-transporting apparatus according to claim 3, further comprising a pressing member formed on the chassis, said pressing member moves into engagement with the second section to position the second section with respect to the first section before the second engagement member engages the first engagement member.
 6. The paper-transporting apparatus according to claim 5, wherein said pressing member moves out of engagement with the second section after the second engagement member has engaged the first engagement member. 